High speed cutting of difficult-to-machine materials with cutting tools coated by Ti-B-C thermally stable films

点击翻译按钮获取中文摘要

We attempt to improve the performance of cutting tools against titanium alloy (Ti-6A1-4V), which is one of the difficult-to-cut materials, by coating of titanium-boron-carbon (Ti-B-C) thin films. We have been prepared the Ti-B-C thin films by DC magnetron sputtering using boron carbide (B_4C) target and titanium target. At first, the deposition experiments were performed with silicon substrates for optimizing the Ti-B-C coating condition. The target power for Ti was varied from O to 200W and CH_4 gas flow rate from 0 to 80 sccm in the deposition process to understand the influences of titanium and carbon contents in the films on the nano-indentation hardness, the frictional properties and the adhesive strength of coatings. Increase of the target power for titanium in the coating process was effective for increasing the adhesive strength of the films onto the substrates. As CH4 introduction in the coating process, the friction coefficient of the films was drastically decreased. Moreover, those films obtained good wear resistant. At the optimized coating condition, the Ti-B-C films were produced on tungsten carbide cutting tools and turning tests were carried out against titanium alloy with the coated tools. The Ti-B-C coating provided improvements in cutting performance against titanium alloys. Tool wear on rake face was decreased by Ti-B-C coating. Chip produced during the turning tests was also smoothed as compared to that formed by the uncoated tool. Surface roughness of workpieces was improved by Ti-B-C coating even in dry cutting.